national aeronautics and space administration … pre-decisional –internal use only –do not...

NASA Pre-decisional – Internal Use Only – Do Not Distribute

National Aeronautics and Space Administration

NASA Exploration Power Distribution SystemsPresented to

S&T Electrical Systems & Wiring Inter-Agency Meeting

Tim Lawrence – Johnson Space Center

December 2015

https://ntrs.nasa.gov/search.jsp?R=20150023257 2018-06-08T06:49:02+00:00Z


Outline

2

• Evolution of Human Exploration Power Systems

• Spectrum of Power Systems and Voltages

• Power Quality

• Aerospace Program EPS Development

• – AMPS Modular Power Components

• – AMPS Standardized Modular Power Interfaces


ISS Deep Space & Mars Risk Reduction Deep Space Port Mars Preparation

Mars/Moon

Missions

Evolution of Human Exploration Power Systems

Initial Exploration Missions Extending Reach Into The Solar System Exploring Other Worlds Planetary Exploration

ISS• Multi-segmented modules

>200kW• Multiple assembly flights

• Chemical propulsion (reboost)

• Load shed tables, basically

manual ops

Space Power: • Multi-segmented modules

>300kW to multi-MW• Multiple assembly flights

• Electric propulsion dominates

• > Semi-autonomous ops

Surface Power:• Multi-segmented power units

>10’s kW each• ≥ Semi-autonomous ops

Space Power: • Multi-segmented modules

>100kW • Multiple assembly flights

• Electric propulsion dominates

• Manual to semi-autonomous ops

Surface Power:• Multi-segmented power units

kW to >10kW each• Manual to semi-autonomous ops

Extended

Missions

Missions: Months

Return: hours

Missions: < year

Return: days

Missions: > years

Return: > months

Near Earth

Missions

3


Spectrum of Power Systems and Voltages

4

Solar Arrays

Batteries

Solar Arrays

Batteries

Fuel Cells

Surface array

Surface nuclear

(Brayton, Stirling)

Batteries

Solar Arrays (0.8 – 2AU)

Nuclear

Batteries

Flywheels

Super-Capacitors

Surface Fuel Cells

Surface array

Surface nuclear

(Brayton, Stirling)

Voltage Standards

28Vdc

120Vdc

160Vdc

Voltage Standards

28Vdc

120Vdc

>300Vdc (electric propulsion)

AC distribution for Brayton or Stirling

Major issue with Rad Hard

Components

Voltage Standards

28Vdc

120Vdc

120Vdc to >300Vdc (electric

propulsion)

AC distribution for Brayton

or Stirling

Complexity and International mix makes it imperative to develop

comprehensive power quality standards from the beginning


What is Power Quality?

5

By Wikipedia –

In its broadest sense, power quality is a set

of boundaries that allows electrical

systems to function in their intended

manner without significant loss of

performance or life. The term is used to

describe electrical power that drives an

electrical load and the load's ability to

function properly with that electric power.

Without the proper power, an electrical

device (or load) may malfunction, fail

prematurely or not operate at all.


Power Quality Lessons

6

• Historically space power systems requirements have been

unique for every platform

– Roadblock for re-use of equipment and standardization

• Majority of the existing power quality specifications were

developed for engine driven alternators for aircraft with AC

transformers and rectifiers for DC.

• Space power systems consist of solar arrays, electrochemical

systems, thermal electric generators, etc.

– All these sources have unique characteristics

• Spacecraft loads are often designed for unique platforms

– Adapted to meet unique voltage ranges and power quality

characteristics

• Common standard allows transportability to a new platform

with high confidence for minimal requalification

• Achieve reliability through verification

– ISS had remarkable success - Pre-assembled flight

elements never tested together were attached to each

other for the first time on-orbit and worked


Characteristics of a Power Quality Standard

7

• Address both Sources and Loads

• Provide a load and source characteristic for

proper operation and protection

• Provide requirement rationale to clarify intent

• Provide verification approach for each

requirement

• Provide typical test procedures

• Allow for design flexibility

• Clearly describe interface (connection) power

for loads

• Specific specifications can then be

developed and coordinated using the

Standard


We now have SAE AS5698 Power Quality Standard

8

Source Requirements• Steady State Voltage Range

• Transient Voltage

• Ripple Voltage

• Stability

• Stability Criteria

• System Impedance

• Power Isolation

• Common Mode Noise

• Voltage

• Current

• Inrush Surges

• Reverse Current

• Fault Clearing

• Fault Coordination

Load Requirements• Operating Voltage Range

• System Voltage

Transients

• System Ripple Voltage

• Stability

• Stability Criteria

• Load Input

Impedance

• Input Isolation

• Common Mode Noise

• Voltage

• Current

• Limiting Inrush Surges

• Limiting Reverse Current

• Overloads

Standard addresses Power Quality for 28 and 120 Volt DC


www.nasa.gov

Aerospace Program for

EPS Development

Advance Exploration System (AES) Program

AES Modular Power Systems

(AMPS) Project


www.nasa.gov

Advanced Exploration Systems (AES) Program

AES Modular Power Systems (AMPS) Project

Objectives:

• Develop modular power units which, when combined with standardized interfaces, can provide commonality across a variety of exploration vehicles.

• Infuse new technology into power systems and components, and prove their capabilities in exploration-based ground demonstrations

Exploration Missions Mars / Lunar Rovers

Planetary Outposts

EVA Suits

Applications


www.nasa.gov

Why modular?

• Flexibility

– Scalable for a wide range of architecture sizes/power levels

– Spectrum of architectures from centralized to distributed

• Reliability

– Failures cause reduced capability, not complete loss of use

– Hot-swap replacement minimizes down-time & system effects

• Deep Space Missions require lower

logistic costs

• Reusability

– Interchangeability between multiple

platforms/missions

– Reduced spare components needed

– Scavenging components from

retired platforms


www.nasa.gov

General

Hierarchical

Architecture

“Monolithic” units can be replaced by

sets of common modules

Solar Array

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Flexible/

Distributed

Architecture

PMAD units containing

mixed modules enable

distributed architectures


www.nasa.gov

Modular Component Development

• Prototypes will drive development of modular standards.

• Batteries and solar cells are already “modular”, so the next step is to develop modular PMAD components:

• Switchgear features:– Remote control

– Fault containment: current limit and trip

• Converter features:– Source/storage/interface/bus regulation

• Common features:– Parallelable to grow in power (“tiers” may be required)

– Digital control, enabling:• Intelligent control / automation at the module level

• Master-less communication for “swarm” intelligence


www.nasa.gov

Solar Array Regulator Development

Objective:

– Demonstrate 5kW 120V Solar Array

Regulator (SAR)

Current Implementation:

– COTS 120V-to-28V converter

– Series-connected boost

configuration: 1kW/module

– Digital control (microcontroller)

• CAN communication (master-less)

• Remote control/fault simulation

• Telemetry

• Dynamic output voltage set-point

(battery charging)

• Intelligence: efficiency optimization

– Hot-swappable enclosure

VIN

VBOOST VIN +

VBOOST

+ +

- -

Series-Connected Boost

AMPS-SOLAR ARRAY REGULATOR

Vicor

Converter

FAN

FAN

FAN

C-RIO

#5

#4

#3

#2

Regulator

Module #1

From

Solar

Array

Simulator

Regulated

Main Bus

Ethernet

NASA-

JSC-DSH

Ethernet

CAN


www.nasa.gov

Solar Array Regulator Development

1 kW Module 5 kW Unit

• Current Status:– Operating in exploration

systems controls lab at JSC

– Regulates bus voltage and bus-tied battery charge current

• Future Work:– Replace power stage with

custom bidirectional module

– Replace microcontroller with FPGA


www.nasa.gov

Switchgear Development

Implementation:

• 1200V/42A MOSFET & shunt

• ADC (sensor) & DAC (driver)

– High speed

– Non-pipelined (low prop. delay)

• FPGA– CAN communication

– Telemetry

– Current limiting

– Thermal trip (power-time curve)

FPGASensors

DriverSwitch

Digital Analog

ADC

DAC

Objective:

Demonstrate a digitally controlled

remote power switch emulating the

characteristics of the state-of-the-art


www.nasa.gov

Bidirectional Converter Development

Objective:

• Demonstrate a 1kW multifunction bidirectional converter

– Battery charge/discharge control

– Spacecraft interface converter

Implementation:

• 120 VIN, configurable output:

– 4 outputs in series: 8.3A @ 120V

– 4 outputs in parallel: 35.7A @ 28V

• Modules can be paralleled

• Topology

– Forward: Full bridge

– Reverse: Weinberg/flyback

– Isolated

– Solar array regulator

– Bus/point-of-load converter


www.nasa.gov

Modular Power Components Summary

• The AMPS project is developing and demonstrating

modular power system concepts for deep-space human

exploration missions.

• Modular power components enable scalable and flexible

power system architectures.

• Three prototypes are in development to assist in

developing modular power standards:

– Solar array regulator (5x1kW modules @ 120V)

– Switchgear (current-limiting to 4A @ 120V)

– Bidirectional converter (1kW @ 120V/4x28V)


www.nasa.gov

AMPS Standardized Modular

Power Interfaces for Future

Space Explorations Missions


www.nasa.gov

AMPS Standardized Modular Power Interfaces

AMPS is drafting a proposed standard that is:

– Applicable to NASA exploration,

– Accommodates variations in power architecture

– Supports mission flexibility (configuration changes)

– Defines the common infrastructure needed to support the

modular design

– Standardizes Data, Electrical and Mechanical Interfaces

The intent is to guide power system developers without

restricting design or technology options.

– Adopts existing standards where applicable

– Emphasize Interchangeability and Interoperability


www.nasa.gov

AMPS Standardized Modular Power Interfaces

• Establish a common framework for Data, Electrical, Mechanical interfaces.

• Apply the Standards to 3 segments of a Power Architecture

• Define interfaces between modules and internal to modules

• Create Interface Specs for– Assemblies,

– Subassemblies

– Components


www.nasa.gov

Standardization Frameworks

• Electrical Interface section addresses modular approach that is flexible, configurable, and supportable

– Breaking an architecture into functional blocks

– Grouping functions as common modular elements

– Creating an interconnection framework of Common Backplanes

– Defining the characteristics that make up Modular Interface Specs

Primary Power Regulation Backplane-Module

Modules mounted on a Assembly Level Backplane.

Unregulated & Regulated Power, Data and Structural and Thermal Interfaces

Modules: Switching, Regulation, Unit Control


www.nasa.gov

Power Assembly Backplanes-ModulesPrimary Power Secondary Power

Main Bus [B]


www.nasa.gov

Additional Standardization Frameworks

• Command & Data Interface section addresses the Communication protocols and Software with emphasis on interoperability standards.– Power modules will support automatic ID, Digital Configuration and

Integration. (i.e. Plug-and-Play)

– Internally, modules adopt protocols suited power applications but must support the higher level Interoperability requirements.

• Mechanical Interface section addresses the mechanical needs in terms of structural support, encapsulation and thermal control.– Modules and backplanes must support static and dynamic loads

while providing a means of transferring thermal loads.

– Mechanical interfaces must assure ease of access and interchangeability.


www.nasa.gov

Acknowledgements

• Walter Santiago

• Jim Soeder

• Larry Trase

• Raymond Beach

• Brent Gardner

• Pat George

• Tony Baez

• James Soeder

• Art Birchenough

• Rich Oeftering

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